The invention provides an integrated two-speed transmission electric drive assembly system and an application method. The integrated two-speed transmission electric drive assembly system comprises a driving motor, a first brake, a second brake, a double-row planetary gear mechanism and a final reduction drive and differential assembly, wherein the output shaft of the driving motor is connected toa front-row planetary carrier through a spline; a front-row ring gear and a rear-row ring gear are integrated into one; a rear-row sun gear is connected to the front-row planetary carrier; steel plateassemblies of the first brake and the second brake are engaged with a gearbox body; a friction plate assembly of the first brake is engaged with an outer ring gear; the friction plate assembly of thesecond brake is engaged with the extension end of a front-row sun gear; and the output end of a rear-row planetary carrier is connected to the input shaft of the final reduction drive and differential assembly and outputs power to wheels. The integrated two-speed transmission electric drive assembly system decreases the axial dimension of a powertrain and decreases the mechanical noise while reducing the difficulty of the arrangement of a whole vehicle. The integrated two-speed transmission electric drive assembly system is compact in whole structure, small in size and light in weight. The design of two-speed transmission enables a motor to work in an efficient range for a long time so as to improve the power performance and economy of the whole vehicle.